426 Nichols and Fraiiklin — Destruction of Passivity, etc* 



The transition was much less clearly marked than at high tem- 

 peratures or within the magnetic field, but repeated trials gave 

 13 co as the amount of water to be added to destroy passivity. 



(J). To 20 cc of concentrated nitric acid at 0°, containing pas- 

 sive iron, water was added, with snow in quantities sufficient to 

 prevent any marked rise of temperature. The addition of 

 172 'S cc of water and snow did not produce noticeable activity. 

 When placed in the field of the electro-magnet (strength of 

 field approximating 20,00011), effervescence began at once, and 

 a dark green solution of higher density than the acid was 

 formed with a brown magnetic precipitation. By a repetition 

 of the experiment outside of the field, it was found that a trace 

 of color could be detected when the acid was diluted to |, and 

 that effervesence began when the strength of acid had been re- 

 duced to j 1 ^. Further reduction to ^ produced no other 

 changes in the reaction, nor did it at any time approach in 

 rapidity that taking place in like circumstances within the 

 field. 



It appears from these experiments that the action of the mag- 

 net is to lower the temperature of transition to the active state, 

 and that the intensity of the magnetic field necessary to con- 

 vert passive into active iron at a given temperature increases 

 rapidly with the concentration of the acid. The establishment 

 of a satisfactory theory of the influence of magnetization upon 

 passivity will probably demand a more complete acquaintance 

 with the phenomena touched upon in this paper, and a wider 

 knowledge than we now possess of the subject of chemical ac- 

 tion in the magnetic field. 



University of Kansas, November, 1885. 



Supplementary Note. 



An investigation of the electric currents set up between rron 

 electrodes within the magnetic field, completed by us since the 

 presentation of this paper, seems to offer a very satisfactory ex- 

 planation of the manner in which the chemical behavior of iron 

 is modified, and its passivity destroyed in the magnetic field. 

 We find that when two iron bars placed parallel to the lines of 

 force in the field are submerged in any liquid capable of attack- 

 ing iron, and when the ends only of one of the bars and the mid- 

 dle of the other bar are exposed to the liquid, the bar with ends 

 exposed becomes in its voltaic relation to the other bar, as zinc 

 to platinum • so that if the bars be connected by means of wires 

 through a galvanometer, a permanent current will be found to 

 flow in the circuit thus formed. 



In the case of a single mass of iron exposed to an acid within 

 the magnetic field, local currents will be set up between those 

 parts of the metal in which magnetic poles are induced and the 



